I spent a lot of time thinking about this at one time. I sleep during the day, and work at night. I figured I would ride at night when it was cool, and sleep during the day. The big advantage of this is that you can go almost any public place and lie down and sleep during the day, and nobody hassles you. If you had a trailer nobody would be even sure you were resting. If you did get bumped, you don't need to pull up stakes just cycle a mile or so, and try again.
But, I hadn't counted on how dark it is in the country. I do not think cycling at night is a good idea in the sticks. And I never really came up with a design I liked. I design wooden ultralight boats, so I think I had a shot, but nothing I really liked came to mind. My best design was like a 2 kid trailer frame, but a composite nose cone was were the kids would be. So it is about half solid. You stuff your gear in there. Then like one of those aluminium lawn loungers, a frame would fold out for your legs to be supported, and a tent extention would keep them dry. But I really wanted an actual trailer.
What about this:
http://www.youtube.com/watch?v=mWnsu4dfNGs
When designing stuff like this, I tried to think not of a teardrop trailer that I could tow, or some other common form. I think there is a novelty version of camper that is an attention getter, but is never going to replace a tent and panniers etc... I tried to think of what my concept was, and what I could design that would supply what I needed. Maybe it ends up looking like a hammock.
In my case I wanted that psychic shelter a solid structure provides. I wanted to have privacy, and I wanted campsite mobility. I think this guy's design would do that. I was thinking of a "coffin" like structure. It has to be as aero as possible, and light to be practical. I specialize in folded plywood forms, so I can dig what he did here. Lots of room for thin solar panels.